Troxler fading is a phenomenon of visual perception that the human brain uses to cope with blind spots on the retina, which is the light-sensitive tissue lining of the inner surface of the eye. One result of this phenomenon is that when one fixates on a particular point, objects in one's peripheral vision will fade away and disappear. Another result related to this phenomenon is the perceived fading of a fixated stimulus when its retinal image is made stationary on the retina, which is otherwise known as a stabilized retinal image. This perceived fading causes the stimulus to fade away after a short time and effectively disappear to the viewer (i.e., the person whose retina is capturing and perceiving the fixed stimulus).
The perceptual fading of stabilized retinal images presents a particularly difficult problem with respect to the navigation of a GUI using a movable indicator whose position is controlled by eye tracking. When eye tracking is accurate such that the movable indicator consistently appears wherever the user looks in the GUI, the movable indicator will be stationary with respect to the user's retina, and as such the movable indicator may fade with respect to the user's perception of the GUI. The perceptual fading of the movable indicator may cause the user to lose track of the location of the movable indicator within the GUI, which lessens the usability of the GUI itself.
When a user loses track of a movable indicator within a GUI, systems typically depend on the user to provide manual input to the GUI in order to remind the user of the location of the movable indicator. However, this is undesirable as it causes the user to become distracted from whatever interaction they are trying to accomplish with the GUI in the first place. Further, such systems do not take into account when the perceptual fading of the movable indicator occurs, and how it can be prevented such that the user does not notice or consider the prevention measure to be a nuisance (e.g., by blocking other information within the GUI or becoming a distraction).